全文获取类型
收费全文 | 35385篇 |
免费 | 4329篇 |
国内免费 | 3028篇 |
专业分类
电工技术 | 3101篇 |
综合类 | 3812篇 |
化学工业 | 4690篇 |
金属工艺 | 2283篇 |
机械仪表 | 2663篇 |
建筑科学 | 2877篇 |
矿业工程 | 1639篇 |
能源动力 | 862篇 |
轻工业 | 4245篇 |
水利工程 | 1167篇 |
石油天然气 | 1291篇 |
武器工业 | 495篇 |
无线电 | 3562篇 |
一般工业技术 | 2967篇 |
冶金工业 | 1273篇 |
原子能技术 | 750篇 |
自动化技术 | 5065篇 |
出版年
2024年 | 227篇 |
2023年 | 710篇 |
2022年 | 1655篇 |
2021年 | 2178篇 |
2020年 | 1506篇 |
2019年 | 1049篇 |
2018年 | 1167篇 |
2017年 | 1279篇 |
2016年 | 1091篇 |
2015年 | 1754篇 |
2014年 | 2136篇 |
2013年 | 2451篇 |
2012年 | 2928篇 |
2011年 | 3260篇 |
2010年 | 2806篇 |
2009年 | 2657篇 |
2008年 | 2856篇 |
2007年 | 2692篇 |
2006年 | 2161篇 |
2005年 | 1635篇 |
2004年 | 1268篇 |
2003年 | 859篇 |
2002年 | 784篇 |
2001年 | 656篇 |
2000年 | 508篇 |
1999年 | 182篇 |
1998年 | 58篇 |
1997年 | 37篇 |
1996年 | 25篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 16篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1959年 | 4篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
低轨互联网星座是当前全球研究和发展的热点,互联网星座支持随遇接入遥感卫星和信息在轨直接处理的应用前景备受期待,但由于轨道高度不同会产生双向高动态异构星座的接入互联问题。首先,通过设定低轨卫星互联网星座在不同轨道特性、不同卫星数量情况下的随遇接入仿真场景,重点探讨了时空非连续可视性和多普勒频移问题对遥感卫星接入性能的影响;其次,基于遥感卫星随遇接入互联网星座场景的特点,分析了不同时延性在轨处理任务的流程及其星地功能分配;最后,对当前在轨智能处理算法存在的问题和未来研究重点进行阐述,为未来低轨互联网星座及遥感卫星的发展和联合组网应用提供可靠的理论支撑。 相似文献
2.
3.
4.
Shuang Chen Chao Yu Zhanfang Cao Xiaoping Huang Shuai Wang Hong Zhong 《International Journal of Hydrogen Energy》2021,46(10):7037-7046
The development of efficient and stable oxygen evolution reaction (OER) catalysts is an ongoing challenge. In order to solve the problem of low oxygen evolution efficiency of the current OER catalysts, a novel material was synthesized by the incorporation of NiFeCr-LDH and MoS2, and its structural and electrochemical properties were also investigated. The introduction of MoS2 improves the electrochemical performance of NiFeCr-LDH. The polarization curve shows that the potential of composite material is only 1.50 V at a current density of 10 mA cm?2, which is far superior to commercial precious metal catalysts. In addition, the stability experiment shows that the composite material has excellent stability, and the current density has little change after 500 cycles. Furthermore, we found that some metal ions, such as Ni, Cr and Mo, exist in the form of high valence on the surface of NiFeCr-LDH@MoS2, which is also conducive to the occurrence of oxygen evolution reaction. 相似文献
5.
6.
Cuiping Yu Shuang Sun Sihui Li Huijia Yan Henan Zou 《International Journal of Food Science & Technology》2022,57(2):1173-1185
In this study, the effect of high-intensity ultrasound (HIUS) (200 and 400 W for 0, 5, 10 and 15 min respectively) on conformational changes, physicochemical, rheological and emulsifying properties of scallop (Patinopecten yessoensis) myofibrillar protein (SMP) was investigated. HIUS-treated SMP had lower α-helix content and higher β-sheet content compared with the native SMP. HIUS treatment induced the unfolding of SMP and increased the surface hydrophobicity. The particle size of SMP decreased and the absolute zeta-potential increased after ultrasonication, which in turn increased the solubility of SMP. The conformational changes and the improvement of physicochemical properties of SMP increased the ability for SMP to lower the interfacial tension at the oil–water interface and increased the percentage of adsorbed protein. As a result, the emulsifying properties, rheological properties of SMP and storage stability of emulsions were also improved. In conclusion, HIUS treatment has future potential for improving the emulsifying properties of SMP. 相似文献
8.
利用纤维床生物反应器(FBB)发酵生产链霉素,对发酵培养基氮源进行了优化,并与传统搅拌发酵进行了比较。结果表明,以可溶性有机氮源大豆蛋白胨作为发酵培养基氮源,并添加一定量蔗糖,可以完全替代黄豆粉,在1 LFBB中发酵96 h时链霉素效价达到5 567 U·mL~(-1)。在整个发酵过程中,所有菌体都被固定在纤维床反应器上,而发酵液保持澄清,这不仅有利于从无菌体的发酵液中进行产物的提取和纯化,也可以重复利用菌体生产次级代谢产物,从而缩短发酵周期,进一步提高链霉素在发酵过程中的体积生产率。 相似文献
9.
Chuntao Lan Haiyang Zou Longfei Wang Meng Zhang Shuang Pan Ying Ma Yiping Qiu Zhong Lin Wang Zhiqun Lin 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2005481
Despite recent rapid advances in metal halide perovskites for use in optoelectronics, the fundamental understanding of the electrical-poling-induced ion migration, accounting for many unusual attributes and thus performance in perovskite-based devices, remain comparatively elusive. Herein, the electrical-poling-promoted polarization potential is reported for rendering hybrid organic–inorganic perovskite photodetectors with high photocurrent and fast response time, displaying a tenfold enhancement in the photocurrent and a twofold decrease in the response time after an external electric field poling. First, a robust meniscus-assisted solution-printing strategy is employed to facilitate the oriented perovskite crystals over a large area. Subsequently, the electrical poling invokes the ion migration within perovskite crystals, thus inducing a polarization potential, as substantiated by the surface potential change assessed by Kelvin probe force microscopy. Such electrical-poling-induced polarization potential is responsible for the markedly enhanced photocurrent and largely shortened response time. This work presents new insights into the electrical-poling-triggered ion migration and, in turn, polarization potential as well as into the implication of the latter for optoelectronic devices with greater performance. As such, the utilization of ion-migration-produced polarization potential may represent an important endeavor toward a wide range of high-performance perovskite-based photodetectors, solar cells, transistors, scintillators, etc. 相似文献
10.